J. Dairy Sci. 85:1482–1490
American Dairy Science Association, 2002.
Digestion, Milk Production, Milk Composition, and Blood Composition
of Dairy Cows Fed Whole Flaxseed1
Helene V. Petit2,3
Dairy and Swine Research and Development Centre,
Agriculture and Agri-Food Canada,
Lennoxville, QC, Canada J1M 1Z3
A total of 90 lactating Holstein cows averaging 628
kg (SE = 8) of body weight (BW) were allotted at calving
to 30 groups of three cows blocked for similar calving
dates to determine the effects of feeding whole un-
treated flaxseed on milk production and composition,
fatty acid composition of blood and milk, and digestibil-
ity, and to determine whether flaxseed could substitute
for other sources of fat such as Megalac and micronized
soybeans. Cows were fed a total mixed diet based on
intake. The experiment was carried out from calving
up to wk 16 of lactation. Cows within each block were
assigned to one of the three isonitrogenous, isoener-
getic, and isolipidic supplements based on either whole
(SOY). Intake of dry matter and change in BW were
similar among diets. Cows fed FLA had greater milk
yield than those fed MEG (35.7 vs. 33.5 kg/d) and there
was no difference between cows fed FLA and those fed
SOY (34.4 kg/d). Fat percentage was higher in the milk
of cows fed MEG (4.14%) than in the milk of those fed
FLA (3.81%) or SOY (3.70%), but milk protein percent-
age was higher for cows fed FLA (2.98%) than for those
fed MEG (2.86%) and SOY (2.87%). Digestibilities of
acid detergent fiber, neutral detergent fiber, and ether
extract were lower for cows fed FLA than for those fed
Feeding FLA resulted in the lowest omega-6-to-omega-
3-fatty-acids ratio, which would improve the nutritive
value of milk from a human health point of view. The
data suggest that micronized soybeans and Megalac
can be completely substituted by whole untreated flax-
seed as the fat source in the diet of early lactating
cows without any adverse effect on production and that
Received November 15, 2001.
Accepted January 10, 2002.
Corresponding author: H. V. Petit; e-mail: firstname.lastname@example.org.
1Contribution Number 726 from the Dairy and Swine Research
and Development Centre, Agriculture and Agri-Food Canada, PO
Box 90, Lennoxville QC, Canada J1M 1Z3.
flaxseed increased milk protein percentage and its
(Key words: flaxseed, milk production, reproduction,
Abbreviationkey: ADFI=AtlanticDairy andForage
Institute, FLA = fat supplement based on whole flax-
seed, MEG = fat supplement based on Megalac, PUFA
= polyunsaturated fatty acids, SOY = fat supplement
based on micronized soybeans.
Dietary polyunsaturated fatty acids (PUFA) are per-
ceived to be healthier than saturated fatty acids. As a
lating the fatty acid profile of milk fat to respond to
consumer demand. Therefore, nutritionists began to
feed cows PUFA, protected against ruminal biohydro-
tion. For example, feeding PUFA such as flaxseed (rich
3 fatty acids in milk fat (see review of Kennelly, 1996),
to meet the guidelines for human health. Flaxseed is
an excellent source of omega-3 fatty acids, which are
diseases, and to increase visual activity (Wright et al.,
1998). Feeding up to 15% of the total DM as flaxseed
has no effect on DMI of midlactating dairy cows (Ken-
nelly and Khorasani, 1992). Flaxseed is also known to
increase concentrations of PUFA in milk, but usually
they do not exceed 3 to 4% of total fatty acids (Kennelly,
1996). Moreover, formaldehyde-treated flaxseed fed at
10% of DM has no effecton DMI of dairy cows compared
with Ca salts of palmitic acid, but it increases protein
and linolenic acid concentrations in milk (Petit et al.,
2001), suggesting a better N utilization on the flax diet.
Oilseeds have generally high concentrations of oleic
and linoleic acids, which are effective antiprotozoal
agents. Dietary supplementation of sunflower seed oil
(6% of DM) to sheep reduced protozoa numbers in ru-
men fluid dramatically within 5 d, from approximately
1 million to fewer than 200,000/ml (Ivan et al., 2001).
Partial defaunation has been reported to increase milk
FLAXSEED AND MILK PRODUCTION
yield by 13.5% and the protein-to-fat ratio by 13.3%
(Moate, 1989). Therefore, oilseeds and oil-rich products
to control protozoa populations in ruminants, and so
to increase the efficiency of dietary protein utilization.
Flaxseed contains approximately 32% oil (Petit et al.,
2001), which would make it a suitable feedstuff to im-
prove utilization of dietary N. There is, however, very
little information on feed utilization of whole flaxseed
by early lactating dairy cows. Therefore, the objectives
of this experiment were to determine feed utilization
and milk production and composition of dairy cows fed
whole untreated flaxseed and to determine if flaxseed
and micronized soybeans.
MATERIALS AND METHODS
The experiment was conducted at the Dairy and
Swine Research and Development Centre, Lennoxville,
QC, from November 1998 to May 1999 using 33 multip-
arous and 15 primiparous lactating Holstein cows.
Cows were blocked within parity for similar calving
dates, and there were 11 blocks of multiparous and five
out from calving up to wk 16 of lactation. Cows were
housed in tie stalls, fed individually, and milked twice
daily at 0545 and 1645 h. Milk production was recorded
at every milking. Milk samples were obtained weekly
from each cow for two consecutive milkings and were
analyzed separately to determine milk composition.
Yield of 4% FCM was calculated according to the equa-
tion of Tyrrell and Reid (1965). Weight and body condi-
tion using a five-point scale (where 1 = emaciated and
for each cow. Cows within groups were assigned ran-
domly to one of three treatments. The three total mixed
diets (Table 1) consisted of fat supplements (Table 2)
based on either whole flaxseed (FLA), Megalac (MEG),
or micronized soybeans (SOY). The three treatments
were designed at the beginning of the experiment to
yield similar CP, ether extract, and NELconcentrations
and were formulated to meet requirements for cows
that were a mean 580 kg of BW and produced 40 kg/d
of milk with 3.5% fat (NRC, 1989). Feed consumption
was recorded daily. Diets were fed twice daily for 10%
orts. Total mixed diets were sampled weekly, frozen,
and composited on a 4-wk basis. Composited samples
were mixed thoroughly and subsampled for chemical
analyses. Silage DM was analyzed weekly for adjust-
ment of the total mixed diets.
Blood was collected from the first 10 blocks of cows
on wk 10 postpartum at 1 h before the morning feeding
Journal of Dairy Science Vol. 85, No. 6, 2002
to give a basal value and at 3 h postfeeding. Blood was
withdrawn from the jugular vein into vacutainer tubes
(Becton Dickinson and Cie, Rutherford, NJ) containing
EDTA for fatty acids, NEFA, and cholesterol analyses
in plasma. The plasma were separated and frozen at
−20°C for subsequent analysis. Milk samples were col-
lected on wk 4 and 8 of lactation from the first 10 blocks
of cows to determine milk fatty acid composition. Total
feces, urine, and milk were collected from the first ten
blocks of cows during wk 12 of lactation for 7 d. Feces
were collected from a rubber mat placed behind the
animals and stored in plastic containers. Daily feces
were weighed and mixed thoroughly. A 10% subsample
was taken and stored at −15°C for subsequent drying
at 55°C. Total urine was collected in stainless steel
containers via Gooch tube (BF Goodrich Co., Kitchener,
ON, Canada) attached to the cow with a nylon netting
covered with neoprene (Spall Bowan Ltd., Guelph, ON,
Canada) affixed to the vulva. A 1% daily subsample
was taken and kept frozen until analysis. Urine was
were obtained from each cow for 14 consecutive milk-
ings and were analyzed for N to calculate N balance.
The experiment was conducted at the Atlantic Dairy
and Forage Institute (ADFI) of Fredericton Junction,
NB, Canada, from September 1998 to April 2001, with
39 multiparous and three primiparous lactating Hol-
stein cows. Cows were blocked as described for dairy
A. The three dietary treatments (Table 1) were similar
to those fed at Lennoxville, and they were formulated
to meet requirements for cows that were a mean 603
kg of BW and produced 40 kg/d of milk with 3.7% fat
ing up to wk 16 of lactation. Cows were housed in tie
stalls, fed individually, and milked twice daily at 0615
and 1530 h. Milk production, milk sampling and analy-
sis, and measurements of BW and DMI were performed
as described for dairy A.
Dry matter of total mixed diets was determined by
drying at 100°C for 48 h. Protein N of silage was ana-
lyzed using an acidified extract (20 g of fresh sample
in 200 ml of 0.01 N HCl, agitated at 21°C for 22 h)
and deproteinized with TCA (Novozamsky et al., 1974).
Nitrogen determinations (N and TCA insoluble N) were
done by the Kjeldahl method (AOAC, 1990). Neutral
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